Systems that handle pressurized fluid, such as fire suppression systems for buildings and other structures, often use the pressurized fluid within the system itself to control the operation of system components, particularly valves, that regulate the flow of the pressurized fluid to the system. In the example shown in FIG. 1, a main valve 10 controlling the supply of pressurized water 12 to a piping network 14 of a fire suppression sprinkler system 16 has a flapper component 18 held in the closed position by a latch 20. Latch 20 is held in contact with flapper 18 by a piston 22 operating within a cylinder 24. The piston 22 is biased by a spring 26 and will move away from and release latch 20 in the absence of pressure within the cylinder 24. Cylinder 24 is in fluid communication with the pressurized water supply 12 through a connector tube 28 extending between the high pressure side of the main valve 10 and the cylinder. As long as there is sufficient pressure in cylinder 24 to overcome the biasing force of spring 26, piston 22 is maintained in engagement with latch 20 and the flapper 18 is held closed.
In response to a fire condition, the pressurized water from supply 12 acting on the piston 22 through connector tube 28 is vented through a vent tube 30 that provides fluid communication between the cylinder 24 and various other valves that open in response to the fire condition. This allows pressurized water from supply 12 to flow through connector tube 28, through the cylinder 24 and out through vent tube 30. If the flow from supply 12 to the cylinder 24 is properly throttled so that water flows at a predetermined flow rate, the pressure within the cylinder will drop, allowing piston 22 to move under the biasing force of spring 26 and release the latch 20. The flapper 18 opens and supplies pressurized water to the piping network 14. The water is discharged from the sprinkler system 16 to fight the fire.
When there is no fire, the pressure within the cylinder 24 should be maintained to keep the latch 20 engaged and the flapper 18 closed even if water pressure from the supply 12 is interrupted. A failure to maintain pressure within cylinder 24 in the absence of pressure from supply 12 will allow the main valve 10 to open during a non-fire event, for example, when pressure is restored, and this is not a desired operating characteristic.
It would be advantageous to have a single device that can be used to control the flow of water through connector tube 28 to ensure that piston 22 moves to allow main valve 10 to open in response to a fire condition, and also maintain water pressure within cylinder 24 in the absence of pressure from water supply 12 and thereby avoid false opening of the main valve during a non-fire event.